© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 1 IP Multicasting: Explaining Multicast

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 2 Objectives  Describe the IP multicast group.  Compare and contrast Unicast packets and multicast packets.  List the advantages and disadvantages of multicast traffic.  Discuss two types of multicast applications.  Describe the types of IP multicast addresses.  Describe how receivers can learn about a scheduled multicast session.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 3 Multicast Overview

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 4 IP Multicast Distribute information to large audiences over an IP network

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 5 Multicast Adoption Past, Present, and Future Multicast ( ) Time Early Adopters NASA, DOD, Cisco, Microsoft, Sprint Financials NASDAQ, NYSE, LIFE, Morgan, GS, Prudential E Learning 150 Universities in US, Hawaii, Oregon, USC, UCLA, Berkley Corporate Communication HP, IBM, Intel, Ford, BMW, Dupont MXU & Content Providers Fastweb, B2, Yahoo, BBC, CNN Multicast Deployment z z z Research Community MBONE Surveillance Law Enforcement and Federal IPv6 Multicast NTT, Sony, Panasonic, Multicast VPN C&W, MCI, AT&T, TI, FT, DT, NTT

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 6 Why Multicast?  Used when sending same data to multiple receivers  Better bandwidth utilization  Less host/router processing  Used when addresses of receivers unknown  Used when simultaneous delivery for a group of receivers is required (simulcast)

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 7 Unicast vs. Multicast

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 8 Multicast Advantages Enhanced efficiency: Controls network traffic and reduces server and CPU loads Optimized performance: Eliminates traffic redundancy Distributed applications: Makes multipoint applications possible

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 9 Other Multicast Advantages  For the equivalent amount of multicast traffic, the sender needs much less processing power and bandwidth.  Multicast packets do not impose as high a rate of bandwidth utilization as unicast packets, so there is a greater possibility that they will arrive almost simultaneously at the receivers.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 10 Multicast Disadvantages Multicast is UDP-based.  Best-effort delivery Heavy drops in Voice traffic Moderate to Heavy drops in Video  No congestion avoidance  Duplicate packets may be generated  Out-of-sequence delivery may occur  Efficiency issues in filtering and in security

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 11 Types of Multicast Applications One-to-many  A single host sending to two or more (n) receivers Many-to-many  Any number of hosts sending to the same multicast group; hosts are also members of the group (sender = receiver) Many-to-one  Any number of receivers sending data back to a source (via unicast or multicast)

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 12 Corporate Broadcasts Distance Learning Training Videoconferencing Whiteboard/Collaboration Multicast File Transfer Data and File Replication Real-Time Data Delivery—Financial Video-on-Demand Live TV and Radio Broadcast to the Desktop IP Multicast Applications

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 13 Self Check 1.List some advantages of multicast transmission over unicast transmission. 2.How does the best effort delivery nature of UDP impact multicast transmissions? 3.What are the 3 basic types of multicast applications? 4.Give examples of one-to-many. 5.What model is used when a host can be a sender as well as a receiver simultaneously?

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 14 Multicast Addressing

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 15 IP Multicast Address Structure IP group addresses:  Class D address (high-order three bits are set)  Range from through

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 16 Multicast Addressing IPv4 Header OptionsPadding Time to LiveProtocolHeader Checksum IdentificationFlagsFragment Offset VersionIHLType of ServiceTotal Length Source Address Destination Address Destination Source Source Address can never be Class D Multicast Group Address (Class D) Multicast Group Address Range Destination (Class A, B, C) Source

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 17 IP Multicast Address Groups  Local scope addresses to  Global scope addresses to  Administratively scoped addresses to

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 18 Local Scope Addresses Well-known addresses assigned by IANA  Reserved use: through (all multicast systems on subnet) (all routers on subnet) (all DVMRP routers) (all PIMv2 routers) , , , and used by unicast routing protocols

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 19 Global Scope Addresses  Transient addresses, assigned and reclaimed dynamically (within applications): Global range: X.X usually used in MBONE applications  Part of a global scope recently used for new protocols and temporary usage

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 20 Administratively Scoped Addresses Transient addresses, assigned and reclaimed dynamically (within applications):  Limited (local) scope: /8 for private IP multicast addresses (RFC-2365) Site-local scope: /16 Organization-local scope: to

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 21 Layer 2 Multicast Addressing IEEE MAC Address Format

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 22 IANA Ethernet MAC Address Range e through e-7f-ff-ff Available range of MAC addresses for IP multicast

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson : : : : : IANA Ethernet MAC Address Range through  Within this range, these MAC addresses have the first 25 bits in common.  The remaining 23 bits are available for mapping to the lower 23 bits of the IP multicast group address. Available range of MAC addresses for IP multicast : : : : :

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 24 Ethernet MAC Address Mapping

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson x0100.5E Multicast MAC Address (FDDI and Ethernet) 32 - IP Multicast Addresses Multicast Addressing Be Aware of the 32:1 Address Overlap IP Multicast MAC Address Mapping (FDDI & Ethernet)

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 26 Madcap in MS Server

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 27 How are Multicast Addresses Assigned? Static Global Group Address Assignment  Temporary method to meet immediate needs  Group range: – Your AS number is inserted in middle two octets Remaining low-order octet used for group assignment  Defined in RFC 2770 “GLOP Addressing in 233/8” Manual address allocation by the admin is still the most common practice.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 28 Learning About Multicast Sessions Potential receivers have to learn about multicast streams or sessions available before a multicast application is launched. Possibilities:  Another multicast application sending to a well-known group whose members are all potential receivers  Directory services  Web page,  Session Announcement Protocol (SAP)

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 29 sdr—Session Directory

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 30 A Cisco IP/TV Example Cisco IP/TV application  Clients (viewers) use program listing Contact the server directly Listen to SAP announcements

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 31 Self Check 1.What is the address range for multicast addresses? 2.What are Local Scope Addresses? 3.What is Mbone? 4.What is the 32-to-1 overlap? 5.What is MADCAP?

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 32 Summary  IP multicast is a much more efficient means of delivering content where a single sender needs to deliver the content to multiple receivers. This task may be achieved through the use of multicast groups.  IP multicasts are designated by the use of a specific Class D IP address range. This is achieved through global scope addresses, which are assigned dynamically, and administratively scoped, which are assigned locally and are reserved for use inside private domains.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 33 Q and A

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 34 Resources  Wikipedia IP Multicast article  Webopedia Mbone article

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 35